Light collimating films, sometimes known as light control films, are known in the art. Such films typically have opaque plastic louvers lying between strips of clear plastic. U.S. Pat. No. Re 27,617 teaches a process of making such a louvered light collimating film by skiving a billet of alternating layers of plastic having relatively low and relatively high optical densities. After skiving, the high optical density layers provide light collimating louver elements which, as illustrated in the patent, may extend orthogonally to the surface of the resulting louvered plastic film. U.S. Pat. No. 3,707,416 discloses a process whereby the louver elements may be canted with respect to the surface of the light collimating film. U.S. Pat. No. 3,919,559 teaches a process for attaining a gradual change in the angle of cant of successive louver elements.
Such light collimating films have many uses. U.S. Pat. No. 3,791,722 teaches the use of such films in lenses for goggles to be worn where high levels of illumination or glare are encountered. Such films also may be used to cover a backlit instrument panel, such as the dashboard of a car, to prevent undesired reflections in locations such as the windshield, or a backlit electronic device (e.g., a LCD computer screen or LCD TV).
U.S. Pat. No. 5,204,160 discloses light collimating films that are formed from a plastic film with a series of grooves formed therein. The grooves are filled with a light absorbing material or the sides and bottoms of the grooves may be painted with a light absorbing ink.
In known collimating films, light management is controlled by an external air boundary. In other words an air layer is required between the output of the collimating film and any other optical films to allow the films to function together. A typical embodiment consists of an assembly where at least some elements of optical film are separated by a layer of air. The optical films are considered separated by a layer of air when the films are not optically coupled or joined by a non-gaseous medium (i.e., a medium other than air). The air layer provides a difference in index of refraction relative to the element which enables the element to perform. However, this air layer between films caused light loss and precludes the use of integrated sub-assemblies.